The 21st century is a generation with rapidly developing technologies. No matter in industries or daily lives, automation is the same direction of development. Correspondingly, the reliance and demand on power have been increasing worldwide. Exhaustion of power has become the issue many developed and developing countries have to face, enabling strategies for renewable energy to be developed.
Currently, solar power generation is one of the main developed renewable energy sources. According to the technology, solar cells are used to receive the solar energy and convert it into electrical energy. A solar cell is formed by joining a p-type semiconductor and an n-type semiconductor to form the positive and negative electrodes. Based on the photoelectric effect principle, the energy of photons separates the positive and negative charges in the semiconductor materials and generating electron-hole pairs. The electrons and holes move towards the positive and negative electrodes, respectively, to generate currents. According to the types of semiconductor materials, solar cells can be classified into single-crystalline silicon, polysilicon, amorphous silicon, III-V compound, and II-VI compound solar cells. Among them, the photoelectric conversion efficiency of III-V solar cells is the greatest. Accordingly, the industry and research institutes devote in optimizing the performance and process of III-V solar cells.
The quality of solar cells determines the performance of solar-cell modules. Because semiconductors are thin and brittle and their fabrication is complicated, structural defects are easily formed during the fabrication process. In order to avoid waste in manufacturing costs as well as improving the yield of end products, defect inspection must be performed before and after modularizing solar cells for guaranteeing the quality and performed of the cells. That is to say, defects should be filtered by exterior inspection and electrical inspection. The items to be inspected include material defects, sintering waves, contamination, micro cracks, and broken fingers. Among them, material defects, sintering waves, and contamination affect apparently the photoelectric conversion efficiency of solar cells. Thereby, their existence can be filtered by electrical inspection.
The electrical inspection method for solar cells according to the prior art adopts a solar simulator to provide a light source with a spectrum close to that of the sun to illuminate the solar cells. Then the voltage and current values generated in the solar cells are measured. According to the data, the solar cells are sorted. Thereby, the performance of the solar simulator will influence the inspection result directly. According to the international standard and regulations, solar simulators can be classified according to radiation luminance, spectral match, intensity uniformity, and instability of irradiance. In addition, the lamp usually adopted in solar simulators is a xenon lamp or a halogen lamp. Although they have great light fluxes and their spectra are close to the spectrum of the sun, they require high-voltage and stable power supplies to maintain their performance, resulting in costly equipment. Moreover, the lifetime of lamps is short, and the filters should be adjusted periodically. Hence, the inspection cost is raised.
In order to reduce the cost of the fabrication as well as improving the efficiency of solar cells, the present invention reduces the cost of inspection equipment by providing a low-cost and rapid electrical inspection method for solar cells.